The present invention relates to a method and an apparatus for folding an airbag that is a component of an airbag module.
U.S. Pat. No. 5,375,393 discloses a method and an apparatus for folding an airbag of an airbag module, in which the airbag to be folded is to be spread out on a platform through which compartment walls can be moved perpendicularly upwards from below. The airbag then lies on the upper ends of the compartment walls, and upright slide means can be pushed into it from above in order to generate the folding. The folded airbag is grasped by a gripper at its outer bag layers, the compartment walls and slide means are withdrawn, and the folded airbag is then turned with the aid of the gripper in order to deposit it in a housing of the airbag module. The method necessitates a relatively complex apparatus for folding and is suitable substantially only for folding the airbag of a driver or passenger airbag module.
U.S. Pat. No. 5,669,204 discloses a method and an apparatus for folding an airbag of an airbag module, in which the airbag is also arranged horizontally. The airbag is guided on a flat, horizontally arranged holding arm. For folding, first the holding arm is withdrawn from the airbag and compartment walls are extended below the airbag vertically from below. Slide means are pushed into these compartment walls vertically from above in order to fold the horizontally placed airbag in portions. Once folding is complete, the airbag is methoded further with the aid of a gripper. The required folding apparatus is again relatively complex, and in particular the threading of the airbag onto the horizontally arranged holding arm is complex.
The present invention provides a method and an apparatus for folding an airbag of an airbag module, in particular a curtain airbag module, in which the apparatus can be of relatively simple construction and at the same time even complex folding can be performed. The apparatuses used hitherto for folding an airbag of an airbag module, with the airbag to be spread out horizontally and the compartment walls and slide means moving vertically, do have certain advantages, at the same time they have certain weak points which can be avoided by an appropriate re-working of the shape of the folding apparatus.
According to the invention, the airbag to be arranged on the apparatus or spread out is arranged with a first portion in a substantially vertical position. This means that the airbag is, at least in part, no longer deposited horizontally on a platform but is arranged for example hanging. This novel type of arrangement of an airbag has the result that when a second portion of the airbag is pushed into a compartment in front of the associated slide means, this second portion is pre-tensioned by the weight of the first, hanging portion.
In the case of conventional folding apparatuses, the airbag is arranged horizontally, with a first portion sliding on a platform or a holding arm and with only the friction of the airbag on the platform or holding-arm surface acting on it in order to slightly pre-tension a second portion of the airbag to be pushed in. According to the invention, by contrast, the entire weight of a first portion of the airbag is used to generate the desired pre-tension. Thus, the apparatus according to the invention can be used to avoid deviations and undesirable transverse folds in the folding to be brought about. Moreover, it is particularly simple to arrange an airbag in a substantially vertical position. Thus, with the method according to the invention, complex laying out of the airbag to be folded on a platform is dispensed with.